Mark Chance said:A DC 15 STR check isn't that hard to make. Many monsters - especially Large or larger ones - have high STR and can easily score a 20, 25, or even higher on a STR check.
Of course, it's a 20 Str check and a 25 Escape Artist check. At low levels, those are difficult. The point about larger creatures generally being stronger is an important one, and such creatures generally have more HD and therefore higher saves. A room full of Medium humanoids will be stuck fast, but a pack of trolls will only be deterred for a few rounds at most.
--Axe